There is intense interest in the programming of insulin-producing pancreatic beta cells for treatment of Type I diabetes, but the mechanism of insulin-producing cell (IPC) specification is not entirely understood. In worms, flies, mice and humans, relatively small populations of insulin-producing neuroendocrine cells are specified in embryonic development;however, invertebrate model systems have not yet been employed to study IPC specification. Our goal is to elucidate the molecular and genetic basis of insulin-producing cell fate specification in Drosophila. Following a study of Drosophila IPC function (Rulifson et al., 2002), we have begun to examine their development. In a pilot genetic screen for IPC lineage expression, we identified several gene enhancer activities in the developing IPC lineage, including: eyeless/Pax-6, dachshund, optix/Six3, and tiptop (teashirt-related). This set of candidate IPC development genes comprises either components or closely related homologues of a conserved transcription factor network for eye specification in Drosophila and mouse. Using eyeless, dachshund and tiptop as molecular markers, we identified a putative IPC progenitor at late embryogenesis. Based on our preliminary observations, we hypothesize that the IPC progenitor is a neuroblast (NB), and that all IPCs are produced from this one NB lineage. We have also found a requirement for eyeless gene function in [PC structure and function, suggesting a concerted role for the other "eye specification" genes we identified in the IPC lineage. We hypothesize that genes expressed within the earliest IPC lineage precursors will have key roles in specification of IPCs. Thus, we have the specific aims: 1) Identify the IPC progenitor and establish its origin;2) Test the hypothesis that the "eye specification" genes are essential for development of IPCs;3) Find additional genes essential for IPC lineage specification. To the best of our knowledge, this will provide the first invertebrate genetic model of IPC developmental mechanisms, significant elements of which will be applicable to beta cell programming in mouse and human systems.